Energy shortages and environmental problems caused by burning large amounts of fossil fuels are aggravating, forcing people to pay more and more attention to exploring new sources of energy and new energy conversion technologies. A low temperature fuel cell, due to its advantages such as high energy conversion efficiency, quick start and non-polluting is known as a class of fuel cell having the most large-scale industrialization prospects. The low temperature fuel cell includes a proton exchange membrane fuel cell, a direct-methanol fuel cell and a direct-acid fuel cell, etc. Catalysts for these fuel cells all use precious metal platinum that is expensive and of scarcity as a main active component, and the resulting high cost of the fuel cell has become a key factor restricting the commercialization of the fuel cell. Meanwhile, as for a commercial Pt/C catalyst that is currently widely used, since only a weak absorption exists between loaded metal particles and a carbon support and the carbon support is easily corroded under an operating condition of the fuel cell, resulting in exfoliation and migration of active metal nanoparticles, seriously limiting a service life of the fuel cell. Therefore, preparation and study of a low-cost, high-activity and high-stability catalyst is of great significance for development and promotion of the fuel cell.
Transition metal nitrides have characteristics such as high melting point, high hardness, corrosion resistance and high electrical conductivity. At the same time, a large number of studies show that nitrides exhibit relatively high activity in some processes of hydrogenation reduction and oxygen reduction and are called “platinum-like catalyst”. Chen et al. used carbon nitride as a hard template to synthesize carbon-supported titanium nitride particles and directly used titanium nitride to catalyze a redox reaction (Ji Chen, Kazuhiro Takanabe, Ryohji Ohnishi, et al. Chem. Commun., 2010, 46, 7492-7494). Although the carbon-supported titanium nitride particles prepared by this technique show certain oxygen reduction activity, its activity is still far away from practical application.
DiSalvo et al. first treated a mixture of zinc oxide and titanium dioxide at 1350° C. for 3 hours, and a sample was taken after cooling and ammonia gas was introduced at 800-900° C. to obtain titanium nitride particles having a particle size of 25-45 nm. By using the titanium nitride particles instead of a catalyst prepared by carbon powder supporting Pt, it was found to have better methanol oxidation performance and stability than the commercial Pt/C catalyst (Minghui Yang, Zhimin Cui and Francis J. DiSalvo, Phys. Chem. Chem. Phys., 2013, 15, 1088). Meanwhile, this research group made use of the same synthesis method to obtain chromium nitride particles with a particle size of 30-50 nm. The Pt catalyst supported by chromium nitride particles showed higher stability than the conventional Pt/C catalyst, and at the same time, an oxygen reduction activity and a methanol oxidation activity were 1.8 times and 1.4 times that of the Pt/C, respectively (Minghui Yang, Rohiverth Guarecuco, and Francis J. DiSalvo, Chem. Mater., 2013, 25, 1783-1787; Minghui Yang, Zhimin g Cui and Franc is J. DiSalvo, Phys. Chem. Chem. Phys., 2013, 15, 7041). However, this method has high requirements on equipment, preparation of samples requires extremely high temperature, and energy consumption is high, while a loading amount of Pt fails to be effectively reduced.
Thotiyl et al. first deposited a layer of titanium nitride on a stainless steel wire by cathodic arc deposition technique to prepare a working electrode, then deposited Pd or Pt metal by a DC deposition method, and thereby prepared a Pt or Pd catalyst supported by the titanium nitride. In an ethanol oxidation experiment, this catalyst showed better catalytic activity and stability than the Pt/C (M. M. O. Thotiyl, T. Ravi Kumar, and S. Sampath, J. Phys. Chem. C, 2010, 114, 17934-17941; M. M. O. Thotiyl, S. Sampath, Electrochim. Acta, 2011, 56, 3549-3554). A method for preparing the catalyst is complicated, an average particle size of the precious metal prepared is 200 nm, and amplitude of increase of activity per unit mass of platinum of the catalyst is very limited.
Chinese patent application No. 200610027287 discloses a preparation technique of an anti-cmosion fuel cell catalyst, wherein Pt was supported on a surface of nitride-supported metal oxide by hydrolysis or vapor-phase themial decomposition, but morphology of the prepared catalyst and performances of the catalyst are not clearly described and provided with relevant proof materials.
In summary, although there have been many efforts to utilize a nitride directly as a fuel cell catalyst and as a carrier for the fuel cell catalyst, one or more disadvantages remain. In the prior art, a related report that a pulse electrodeposition method is used to directly deposit a thin active metal layer on a surface of inexpensive transition-metal nitride nanoparticles to prepare a catalyst suitable for fuel cell with a particle size within 10 nm has not been found.